This invention relates to reflective ultrasonic imaging systems, and more particularly to a steered beam multi-sector ultrasonic scanner and imager with real-time display capability.
Most B-scan ultrasonic systems in medical operations utilize a manually held transducer that is slowly translated along a chosen path, at the same time being rotated in the scan plane. These instruments have the two basic disadvantages of slow operation and poor repeatibility.
A cardiac scanner developed by F. L. Thurstone et al is based on the phased array and electronic focusing techniques proposed by V. G. Welsby et al. This single-sector steered beam instrument has a linear transducer array and generates an acoustic beam oscillating over a 60.degree. sector centered on the midpoint of the array. Real-time images at 20 frames/sec. are produced, but the system is hampered in the detection of specularly reflecting targets. This device is explained in the article "A New Ultrasound Imaging Technique Employing Two-Dimensional Electronic Beam Steering" by Thurstone and von Ramm, Acoustical Holography, Vol. 5, 1974, Plenum Press, New York, pp. 249-259. The basic limitation of this technique resides in the fact that for a given relfecting surface each point is insonified in only one direction defined by the line from the point to the center of the array. The probability of proper display of a randomly oriented surface increases when each point of the surface is scanned from different directions. This requires moving the origin of the scanning sector.